This invention relates to a brake pressure modulator having a pressure sensing manifold for sensing master cylinder braking pressure.
Modern passenger cars and light trucks are equipped with split circuit hydraulic brakes in which the vehicle operator generates braking pressure in primary and secondary braking circuits by operating a brake pedal connected to a master cylinder (usually through a booster that amplifies the force applied by the vehicle operator). More recently, vehicles have commonly been equipped antilock braking systems (ABS), traction control systems (TCS), and vehicle stability control (VSC). Adaptive cruise control (ACC) and panic brake assist (PBA) systems have also been proposed. All of these systems require a brake pressure modulator connected in the primary and secondary braking circuits to control braking pressure communicated to the vehicle brakes. The modulator is equipped with an electronic control unit (ECU), which generates electronic control signals controlling the braking pressure. Commonly, actual master cylinder braking pressure in the primary and secondary master cylinder braking circuits is not sensed. However, it is desirable that the actual braking pressure being developed at the master cylinder be sensed and used by the ECU to control braking pressure.
However, direct sensing of braking pressures has associated cost and reliability considerations. For example, such sensors require separate fluid connections in the braking system, thus creating potential leakage points; require extra assembly operations when the vehicle is manufactured, since the pressure sensor must be installed separately; and require an additional external power connection as well as connections transmitting the signal or signals representing braking pressure. It has also been proposed that pressure sensors be mounted directly on or in the master cylinder itself, but such sensing would still require additional external electrical connections.
According to the present invention, a pressure sensor or sensors are mounted in a manifold which is installed directly on the modulator housing when the modulator is manufactured. The pressure sensors receive power and are grounded through the electronic control unit which is an integral component of the modulator; accordingly, the sensors do not require external electrical connections other than those already provided on the modulator. Since the sensing manifold is installed and tested for leaks when the modulator is manufactured and before the modulator is shipped to the vehicle assembly plant, assembly operations in addition to those required in installation of the modulator in the vehicle braking system are not required.